Few classic Dad Jokes, and few very fresh

Why makes this Joke funny?

1. What do sprinters eat before a race?

This joke plays on the double meaning of fast: one meaning to abstain from eating and the other referring to moving at high speed.

2. I tell dad jokes...

Faux pa sounds like faux pas (a social blunder) and also plays on pa (informal for father). Faux means fake. So, a faux pa is a fake dad, making dad jokes.

3. I changed all my passwords to Kenny...

This joke is a play on the name Kenny Loggins (the musician) and logins (as in logging into an account). All Kenny Loggins sounds like all key logins.

4. What did the duck say when he bought the chap-stick?

The joke lies in the double meaning of bill: a duck’s bill (part of its anatomy) and a bill as in a tab or invoice.

5. I dreamt last night that I was a muffler...

The joke plays on the word exhausted meaning both being very tired and referring to a part of a car`s exhaust system (which includes the muffler).

6. A friend had a new baby girl...

The humor in this joke stems from the play on words and the unexpected interpretation of the name.
When the friend says the baby`s name is "Melanie Noelle," most people would think the first name is "Melanie" and the middle name is "Noelle." However, when the coworker asks, "How do you spell it, then?" it humorously implies that the name is "Melanie No L," where "No L" is a phonetic way of saying "Noelle."
It`s the twist and the misinterpretation of "Noelle" as "No L" that gives the joke its punchline.

7. I spent all my money collecting every bird species...

This joke involves a play on words: egrets (a type of bird) is phonetically similar to regrets. So, the speaker is saying they have no egrets/regrets about the situation.